A heart pacemaker is generally implanted subcutaneously in the chest wall along with a coiled structure such as an electrical wire coil lead for conducting electrical signals such as stimulating and sensing signals between the pacemaker and the heart. The lead is surgically implanted through a vein leading to a cavity of the heart. A typical lead includes one or more helical wire coils having a hollow inner passageway that extends the entire length of the wire coil. The coiled structures are positioned in the lead either coaxially or laterally. The wire coils are surrounded by an insulating material such as a flexible tube, sheath, or coating comprising, for example, silicone or polyurethane for insulating the wire coils from body fluids as well as each other. However, one problem is that, over time, fibrotic tissue commonly encapsulates the pacemaker lead especially in areas where there is low velocity blood flow. When small diameter veins through which the lead passes become occluded with fibrotic tissue, separating the lead from the vein is difficult and causes severe damage or destruction of the vein. Furthermore, the separation is usually not possible without restricting or containing the movement of the pacemaker lead.
In most cases, the useful life of a pacemaker lead lasts for many years. However, should the pacemaker lead become inoperative or should another heart lead be desired, the existing pacemaker lead is typically left in place, and a new pacemaker lead is implanted. One problem with leaving an implanted lead in place, particularly in the heart, is that the lead actually restricts the operation of the various heart valves through which the lead passes. If several leads passing through a heart valve are left in place, the operation of the heart valve and the efficacy of the heart is significantly impaired.
Another problem associated with leaving a pacemaker lead in place, particularly in blood vessels, is that an infection may develop in or around the lead, thereby requiring surgical removal. Surgical removal of the lead from the heart often involves open heart surgery with accompanying complications, risks, and significant cost.
One method for transvenous removal of a pacemaker lead involves a prior art heart lead removal tool that utilizes a hollow, rigid tube and a beveled rod tip for engaging and deforming the coiled structure of the heart lead. However, when the lead cannot be removed because of some complication, a serious problem is that the tip of the tool is locked in place and cannot be removed from the lead. As a result, the tool and lead must be surgically removed. Furthermore, the rigid tube of the tool can easily puncture a blood vessel or, even worse, a heart cavity wall.
Another method is to transvenously extract the lead manually without the aid of a tool. Such method is possible only when the lead has not been encapsulated in or restricted by a blood vessel. Even then, this method has a number of problems. First, when the polyurethane or silicon insulation surrounding the wire coil is damaged, the insulation can sever and cause the coiled structure of the lead to unwind and possibly to damage the heart and surrounding blood vessels. Secondly, when both the coiled structure and insulation are severed in the heart or a blood vessel, surgical removal is required. Thirdly, most pacemaker leads typically include tines or a corkscrew at the tip or a conically shaped tip for securing the distal end of the pacemaker lead to a heart cavity wall. For fibrotic tissue that has encapsulated the tip, unaided manual removal of the heart lead from the heart cavity wall may cause an inward extension or inversion of the wall, or even worse, permanent damage to the heart such as tearing a hole in the heart cavity wall.
There a several different systems for lead removal that involved advancing a stylet into the coiled electrode and securing the electrode near the tip of the lead to facilitate its removal. The LEAD EXTRACTION™ System (Cook Vascular Inc., Leechburg, Pa., described U.S. Pat. No. 4,988,347, entitled “Method and Apparatus for Separating a Coiled Structure from Biological Tissue”, Filed Nov. 9, 1988, and related subsequent patents) is particularly well-suited for the removal of a pacemaker lead implanted in the heart and encapsulated in vessels connecting with the heart. Others devices by Vascomed and Spectranetics have entered the market in the U.S. and/or Europe. While the use of a radially expandable wire coil at the distal end of a stylet is an effective method of securing the pacemaker lead near the electrode tip, failure to engage has been observed in a number of cases. In an expandable wire coil system, correct sizing of the lead coil is critical prior to introduction of the locking stylet. Nevertheless, behavior of the wire coil during expansion can be unpredictable so that even when the correct locking stylet is selected, adequate engagement with the lead coil often cannot be achieved, or the two can separate during traction to free the lead. While often this may occur due to improper locking technique on the part of the physician, often the failure is purely mechanical. Many times, a second locking stylet can be used successfully, but this results in increased material costs and risk to the patient due to the lengthening of the procedure.
Another disadvantage of currently available systems is that array of different sized stylets must be used for the wide range of pacemaker electrode sizes, normally 0.016 to 0.032'″. Having to properly size the coil for selection of the optimal stylet adds time, cost, and the potential for error to the procedure. What is needed is a single locking stylet that can expand to engage and remove any standard pacemaker lead, regardless of the electrode coil size.